1. Field of the Invention
This invention relates to a system adapted to display a visual field of a surgical microscope, which is used when operating a very small region in brain surgery, ophthalmology, otorhinology or the like, on an enlarged scale on a video monitor or to take a still picture of the visual field by a single action. The above system will hereinafter be called a "TV-photography system".
2. Description of the Prior Art
FIG. 1 is a schematic illustration of optical paths when a still photographic camera is combined with a surgical microscope. Light from a very small region 1, which is now under operation, travels through objective lenses 2a, beam splitter 3 and surgeon's eyepieces 5, all of which are provided with a main barrel 2 of the surgical microscope, to surgeon's eyes 5. A luminous flux which has been divided out by the beam splitter 3 and is shown at the lefthand side in the drawing runs through an assistant's eyepiece 6 and reaches the eye 7 of an assistant. On the other hand, a luminous flux which is shown at the righthand side in the drawing is adjusted in luminous energy by a diaphragm 8a of an imaging adapter 8 and then focused on a film surface 9a of a still photographic camera 9. A surgery must be carried out in an completely sterilized environment. It is however difficult to sterilize such a surgical microscope and camera completely. Therefore, the surgical microscope and camera are covered in their entirety by a sterilized drape 10 upon making a surgery, except for portions where the objective lenses and eyepieces are respectively located. In the above construction, the very small region, which is now under operation, is visible by the surgeon and his assistant only. In order to show the very small region to other staff in the operation room and/or observers at the same time, a television camera (not shown) is usually provided instead of the still photographic camera 9. The television camera is arranged in such a manner that its target assumes the position of the film surface 9a. When it had become necessary to record the details of a surgery on a still picture, it was conventionally required to interrupt the surgery for replacement of the television camera with the still photographic camera. It was a very difficult work to replace the television camera by the still photographic camera and, after taking a still picture, to put back the television camera within the sterilized drape 10, while paying attention to avoid any contamination of the sterilized drape 10.
With a view toward overcoming the drawback of the above-mentioned prior art system, it has been attempted, as depicted in FIG. 2, to provide an operable mirror (swingable mirror in this embodiment) 8b' with the imaging adapter 8 and, when taking a still picture, to manually swing down the mirror to a position indicated by 8b, thereby focusing an image on the film surface 9a of the still photographic camera 9. However, it does not only require special attention but also is unavoidable to interrupt the surgery for a long period of time to operate the imaging adapter 8 surrounded by the drape 10 so that the mirror is first of all swung down to the position indicated by 8b, to adjust the diaphragm 8a to a value suitable for still photography, and, after taking a still picture, to return the diaphragm 8a and mirror 8b to their normal value and position respectively.